[RFI] 160m arcing noise question

[Sam Morgan]

I have an interesting one for the group. About 6:30am while listening to a 
morning group on 1.900mhz. I started hearing an arcing sound. The arcing was 
heard all the way from 1.8-2.0mhz. at an S9+20 on both my vertical and my 
dipole. I was able to kill it by setting my K3's noise blanker to IF Medium 1 or 2.

The noise lasted from 6:30am until about 7:15am. It was mostly steady but did 
stop and start every now and then. This is in W. Texas, we have had only on inch 
of rain this entire year, so waiting to see if it stops when the next rain 
washes the insulators, isn't really a good option, hi hi.

Now it gets interesting, I switched to 80m and the arcing was not there. I tried 
both antennas but there was no arcing heard anywhere on 80m.

So. any suggestions what kind of noise source would be evident on 160m only?

30sec 5meg wave file of the arcing can be heard here:
http://k5oai.com/rfi/2011/audio/04202011-1201z-1.9mhz_arcing.wav

P.S.
Maybe a clue? I have heard something like this before, usually in the mornings 
around 7am, and would only happen once or twice for a brief 10-20 sec duration.

TIA
-- 
GB & 73
K5OAI
Sam Morgan